The present invention relates to the general field of stationary ring assemblies for gas turbines. It relates more particularly to stationary ring assemblies for turbomachine high-pressure turbines when the assemblies are of the type constituted by a plurality of segments joined end to end with sealing strips interposed therebetween.
In a gas turbine, e.g. a turbomachine high-pressure turbine, the rotor-forming moving blades are surrounded by a stationary ring assembly forming a shroud. The stationary ring assembly thus defines one of the walls of the flow path for the hot gas coming from the combustion chamber of the turbomachine and passing through the turbine.
The stationary ring assembly is made up of a turbine ring fastened onto the casing of the turbine by means of a spacer. In general, the ring and the spacer of such a stationary ring assembly are in the form of sectors, i.e. they are each made up of a plurality of segments joined end to end.
Since the stationary ring assembly defined in this way is in direct contact with the hot gas coming from the combustion chamber, it is necessary to cool the various segments which make up said assembly. To this end, air taken from the end of the combustion chamber flows into a cooling circuit formed in each segment of the stationary ring assembly and is exhausted into the gas flow path, upstream from the moving blades of the turbine.
It is also necessary to provide sealing between the adjacent segments of the stationary ring assembly so as to avoid air leaks that are particularly detrimental to good cooling of the segments. To this end, it is known to interpose sealing strips between the adjacent segments. Such strips are generally received in facing axial and facing radial slots formed in the adjacent side faces of the segments. They thus serve to obstruct the clearance that exists between two adjacent segments, so as to limit air leaks regardless of the amount of thermal expansion to which the segments are subjected.
The radial and axial slots in which the sealing strips are received are generally machined so that they are contiguous, i.e. so that they communicate with one another. This arrangement is made necessary by the fact that the sealing strips must maximize the area they cover of the side faces of the segments so as to obtain good sealing.
However, in practice, it should be observed that such an arrangement of the slots generates significant air leaks at the junctions between the axial and radial slots. Such leaks are shown in FIG. 5. In this figure, two segments 100, 100′ of the stationary ring assembly are shown in part, each segment being provided with an axial slot 102, 102′ and with a radial slot 104, 104′. The clearance 110 that exists between the strips and the slots results from the fact that, since the segments are exposed to the hot gas coming from the combustion chamber, they are subjected to thermal expansions and contractions which are passed on to the clearance 112 that exists between the two adjacent segments.
As a result of the distribution of pressure in the cooling circuit of the segments 100, 100′, air leaks occur at the junctions between the axial and radial slots 102, 102′ and 104, 104′ (the leaks are shown by shading in the figure). Such leaks are particularly detrimental to the cooling of the segments and to the efficiency of the turbine.